Interfacing an optical fiber to an optical source is referred to as pigtailing. In the past, optical designers have not successfully solved the problem of providing a simple, lightweight, economical interface between an optical source and an optical fiber. Of the methods used in the past, they have been successful in the laboratory and in relatively benign environments only.
Those working in the art have been unable to demonstrate a rugged, shock-hardened pigtail device for an optical source.
A substantial need for a method of interfacing optical fibers to optical sources has developed in the fields of fiber optic sensors and communications systems. A typical application for such a device which is shock-hardened and capable of operation in wide temperature ranges is a fiber optic gyro for smart munitions and/or missiles used by the military. Commercial applications also exist whereby a solid, simple interface is desired.
It is known in the prior art to use grooves in a substrate to join optical fibers together. The grooves are used to align and secure the optical fibers. See an article, "Fiber Connectors, Splicers and Couplers" by Kao and Bickel, ITT Electro-Optical Products Divisions, Roanoke, Va. The use of tapered optical fiber in making connections to lithium niobate (LiNO.sub.3) is known as taught by U.S. Pat. No. 4,445,571 (Divens et al.). This, however, is in the art of coupling lithium niobate substrate waveguide devices to optical cables, and is not for interfacing to an optical source such as a laser.
Optical fibers coupled to integrated optical (I/O) devices made of lithium niobate are well known in the art. Generally, these devices are large, complex and are sensitive to shock and vibration forces and are similar to known devices for pigtailing to an optical source. An I/O device coupled to an optical fiber in a superior manner is disclosed in U.S. Pat. No. 4,750,800 assigned to the same assignee as this application. That patent discloses the use of a fiber optic carrier in combination with the I/O device and the optical fiber. The fiber carrier is made of a material which has a coefficient of thermal expansion in the plane of the substrate mounting surface which is substantially equal to the coefficient and expansion of the I/O chip. In that patent it is also disclosed that the fiber carrier may be of the same material as the I/O chip. The I/O device and the fiber optic carrier are attached by the use of epoxy resin.
Prior art devices known to Applicants for interfacing an optical fiber to an optical source generally include large complex clamping devices which are mounted on a base along with the light source. See, for example, the advertisement on page 32 of the August 1986 issue of Fiber Optic Product News for a high reliability laser diode made by Stantel Components, Inc. For further examples, see part specification QLM1550FM for a Diode Laser Module made by LASERTRON of Boston, Mass., USA and part specification FU-43SLD-2 for a Laser Diode Module made by Mitsubishi of Japan.